Question

1. Consider the following sequence (5’ – GUCCAUCA – 3’) that represents a segment of the mRNA produced by a virus. Suppose the virus was a negative-strand RNA virus. What would the corresponding genomic sequence be?

   1. 5’ – GUCCAUCA – 3’

   2. 5’ – GTCCATCA – 3’

   3. 3’ – CAGGTAGT – 5’

   4. 3’ – CAGGUAGU – 5’

   5. None of the above

Answer 1

Answer -  3’ – CAGGUAGU – 5’

Explanation - The negative-sense viral RNA is complementary to mRNA (messenger RNA) like DNA and the positive-sense viral RNA nucleotide sequence is similar to that of mRNA .

Segment of mRNA = 5’ – GUCCAUCA – 3’

The mRNA is complementary to RNA (RNA is negative sense).

The nucleotide sequence of RNA = CAGGUAGU

Uracil is present in RNA instead of thymine nitrogen base that present in DNA. The RNA should have 3' - 5' polarity, because the negative-sense (or antisense) RNA sequence and mRNA sequence are complementary with each other.

So, the RNA sequence will be - 3’ - CAGGUAGU - 5’